Transferring data of contents, such as an image, music and a video, between two apparatuses having a USB (Universal Serial Bus) interface and mutually connected via a USB cable or the like is an operation that is commonly performed.
One of the two apparatuses performing data transfer is a USB host managing connection between the apparatuses, and the other is a USB device in accordance with management by the USB host. As a concrete example of an apparatus to be the USB host, a personal computer is used. As a concrete example of an apparatus to be the USB device, a digital camera, a digital photo frame, a mobile music player or the like is used.
Connection between the USB host and the USB device is enabled when the apparatuses are electrically connected via the power line and signal line of a USB cable or the like and disabled when at least one from among the power line and signal line is electrically disconnected.
The USB device has a function of, when connection with the USB host is enabled at the time of transferring data, giving priority to an operation from the USB host and locking the USB device to disable an operation on the USB device, in order to prevent malfunction and damage to data due to conflict between operations.
Therefore, in order to operate the USB device after finishing data transfer, it is necessary to disable connection with the USB host, for example, by pulling out the USB cable, and this becomes a troublesome operation.
In Patent Literature 1, a method for enabling an operation of an USB device (digital camera) connected to an USB host (printer) via a USB cable is described.
According to the method described in Patent Literature 1, in the case of performing data transfer, the connection between the printer and the digital camera is enabled by a user's operation, such as pressing a button of the printer. The digital camera transfers data obtained by image-taking by the user to the printer. When the data transfer ends, the printer electrically disconnects the power line of the USB cable to disable connection with the digital camera.
Since connection between the USB host and the USB device is not enabled except while data transfer is performed, it is possible to operate the USB device, even if the USB device is connected to the USB host via the USB cable.
Recently, an information transfer system has been popularized which is provided with a server that distributes contents, an information presentation apparatus that presents (displays/reproduces) the data, and an information transfer apparatus that transfers the data distributed from the server to the information presentation apparatus.
If, in the case of performing data transfer between the information transfer apparatus and the information presentation apparatus, the method described in Patent Literature 1 is applied, with the information transfer apparatus and the information presentation apparatus functioning as a USB host and a USB device, respectively, it is possible to operate the information presentation apparatus even if the information presentation apparatus is connected to the information transfer apparatus via a USB cable, because connection between the information transfer apparatus and the information presentation apparatus is not enabled except while data transfer is being performed.